Thread cutter in sewing machine

ABSTRACT

An improved thread cutter in a sewing machine including a reciprocative thread cutter blade and thread holder member both disposed above shuttle race means so as to work in coordination with each other, the thread cutter blade being capable of simultaneously cutting both the upper and under threads of the sewing machine while the threads are held under tension by the thread holder member. The thread cutter blade and the thread holder member are respectively coupled with a pair of rotary members which are respectively turned round by means of a pair of shaft-mounted sliders energized with an elastic member. Actuated by a solenoid and the like, the thread cutter blade and the thread holder member are thus moved from their standby positions on one side above the shuttle race means to the other side thereof and, en route, get hold of the upper and under threads together. Thereafter the threads held by the thread holder member is severed by the thread cutter blade that has then started moving rapidly back to its initial position. And only after the severance of the threads is the thread holder member permitted to return to its initial position in succession to the thread cutter blade.

United States Patent [72] Inventor l-litoshlsakashita Kariya, Japan [21] ApplvNo. 21,751 [22] Filed Mar. 23, 1970 [45] Patented Aug. 31, 1971 [73] Assignee Aisin Seiki Kabushiki Kaisha Kariya-shi, Aichi-lren, Japan [32] Priority Mar. 24, 1969 [33] Japan 1 l l 44/21707 [54] THREAD CUTTER 1N SEWING MACHINE 7 Claims, 12 Drawing Figs. I 52 us. Cl 112/252 [51] Int. Cl l D05b 65/00 [50] Field ol'Search :112/252 [56 1 References Cited UNITED STATES PATENTS 3,386,402 6/1968 Ross 112/252 3,424,116 l/1969 VonHagen 1 12/252 3,424,117 H1969 Schopf 112/252 3,470,835 10/1969 Saganowich et al. 1 12/252 3389 15 1/1970 Marforio ABSTRACT: An improved thread cutter in a sewing machine including a I reciprocative thread cutter blade and thread holder member both disposed above shuttle race means so as to work in coordination with each other, the thread cutter blade being capable of simultaneously cutting both the upper and under threads of the sewing machine while the threads are held under tension by the thread holder member. The thread cutter blade and the thread holder member are respectively coupled with a pair of rotary members which are respectively turned round by means of a pair of shaft-mounted sliders energized with an elastic member. Actuated by a solenoid and the like, the thread cutter blade and the thread holder member are thus moved from their standby positions on one side above the shuttle race means to the other side thereof and, en route, get

hold of the upper and under threads together. Thereafter the threads held by the thread holder member is severed by the thread cutter blade that has then started moving rapidly back to its initial position. And only after the severance of the threads is the thread holder member permitted to return to its initial position in succession to the thread cutter blade.

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sum 3 or 4 INVENTOR Hire sm' J4 :msm'rn ATTORNEYS THREAD CUTTER IN SEWING MACHINE BACKGROUND OF THE INVENTION This invention relates to an improved thread cutter in a sewing machine. More specifically, the invention relates to a thread cutter in a sewing machine whereby both the upper thread (i.e., the thread leading to the sewing machine needle) and the under thread (i.e., the thread leading to the shuttle bobbin) are cut simultaneously at a position above shuttle race means, with only minimum lengths of the threads left at the end of the seam they have made.

The cutting of the threads by means of scissors is as troublesome to the machine sewer as it is frequent. In order to overcome this practice which greatly hampers the progress of sewing work, there have already been advocated a variety of thread cutting devices to be built into sewing machines. Yet every one of these has some drawback or another. In one of such devices, for instance, the upper and under threads are cut separately, the upper thread by means of a cutter blade attached to a presser foot and the under thread by means of I another cutter blade disposed below a throat plate. The trouble withthis type of thread cutting device is that the presser foot has to be redesigned exclusively for the purpose. Moreover, the two cutter blades need their own separate drive units, which not only complicate the mechanisms of the sewing machine but make it more costly.

in another example somehow closer to the present invention, the upper and under threads are cut simultaneously beneath the throat plate, usually by means of a stationary cutter blade to which the threads seized by a thread catcher is guided, or by means of a pair of movable blades working as scissors. In these devices, too, there have frequently been caused such troubles as the failure to cut the threads due to the difficulties involved in the adjustment of a distance between the cutter blade and the threaded catcher, and the ready damage of the blades.

SUMMARY OF THE INVENTION It is a primary object of the invention .to provide an improved thread cutter in a sewing machine so simplified in construction as to consist essentially of a thread'cutter blade and thread holder member alone, which work in close coordination to simultaneously cut both the upper and under threads of the sewing machine. 7

Another important object of the invention is to provide an improved thread cutter in a sewing machine which hardly ever fails to cut the threads since they are held under tension by the thread holder member when about to be cut by the thread cutter blade.

Still another important object of the invention is to provide an improved thread cutter in a sewing machine whose thread cutter blade and thread holder member are shaped specially to insure the unfailing cutting of the threads.

Yet another important object of the invention is to provide an improved thread cutter in a sewing machine whereby the threads are cut in such a manner that only minimum lengths thereof are left at the end of the seam whereas the remaining upper and under threads are ready for the succeeding sewing work without any rearrangement.

Yet a further important object of the invention is to provide an improved thread cutter in a sewing machine which works on one, or two if desired, drive unit.

A further still important object of the invention is to provide an improved thread cutter easily adoptable in conventional sewing machines, without need for the provision of any specially designed presser foot, shuttle race means, feed dog, tension release and the like.

With these objects in view and the other objects hereinafter set fort, the present invention will now be described in detail with reference to the accompanying drawings showing a specific embodiment thereof, wherein like reference characters indicate like parts throughout the several Figures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a bottom view of part of the bed of a sewing machine incorporating the thread cutter of the invention;

FIG. 2 is a partially cutaway front view of the sewing machine bed of FIG. 1;

FIG. 3 is an enlarged sectional view taken'along a plane of line A-A in FIG. 1;

' FIG. 4 is a side view showing in detail a drive unit of a thread cutter blade and thread holder member of the invention;

FIG. 5 is a sectional view of the driven unit of FIG. 4, showing its internal structure;

FIG. 6 is an explanatory view showing the positions of the thread cutter blade and thread holder member when the thread cutting mechanism is kept standing by;

FIG. 7 is an explanatory view showing both the looped upper thread and the under thread seized by the thread cutter blade and thread holder member as they start working;

FIG. 8 is a perspective view of FIG. 7;

FIG. 9 is an explanatory view showing the thread cutter blade and thread holder member as they are made ready for cutting the threads;

FIG. 10 is a perspective view of FIG. 9;

FIG. 11 is an explanatory view showing the relative positions of the thread cutter blade and thread holder member immediately after cutting the threads; and

FIG. '12 is a perspective view of FIG. 11.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, a frame piece 2 beneath a bed 1 is secured in place by a pin 5 doubling as a setscrew of a bush 4 of a feed rockshaft 3, and by a clamp screw 6 also serving asa leg of the bed 1. Another frame piece 8 is secured to another leg 7 of the bed by means of a clamp 9 and a clamp screw 10. Extended between the frame pieces 2 and 8 is a shaft 11, which is secured in place by means of screws 12 and 13. Sliders 14 and 16 are mounted on the shaft 11, the slider 14 being rotatably coupled with a link member 17 by means of a hinge screw 16. At the other end, the link member 17 is rotatably coupled with a lever 19 by means of a screw 18, and the lever 19 is pivoted at the frame piece 2 by a pin 20.

As illustrated in FIG. 5, the shaft 11 is hollowed, with a hole 11a running lengthwise therethrough, and is provided with a cutout slot 11b in the wall thereof thus formed by the hole 11a. The above-mentioned hinge screw 16 connecting the slider 14 to the link member 17 is provided with a leg portion 16a, which is loosely inserted into the cutout slot 11b, whereby the slider 14 is guided longitudinally of the shaft 11 without turning round. Also, an arm 22 having a pin 21 is secured to the slider 14 by means of a screw 23. Similarly, an arm 25 having a pin 24 is secured to the other slider 15 by a screw 26, and the slider 15, too, like the foregoing slider 14, is guided securely along the shaft 11 by means of a hinge screw 27 having a leg portion 27a.

Two rotary members 30 and 31 are mounted at the end 29a of a bush 29 pivotally supporting an oscillating shaft 28, and the rotary members 30 and 31 arefprevented from moving in the longitudinal directions of the oscillating shaft 28 by means of a wave washer 32 and stop ring 33. The two rotary members 30 and 31 are respectively attached with a thread cutter blade 34 and a thread holder member 35 by means of screws 36 and 37, respectively. Moreover, the two rotary members 30 and 31 have cutout slots 30a and 31a, respectively, into which the pins 21 and 24 mentioned above are slidably inserted. As a result, the thread cutter blade 34 and thread holder member 35, both directly concerned with the desired thread cutting operation, are capable of revolving concentrically with the oscillating shaft 38 in the vacancy between shuttle race means 38 and a feed dog 39.

The reference numeral 40 designates a table of the sewing machine, to the lower surface of which are screwed a solenoid 41 and a support 45 pivoting a link member 44 by means of a pin 42 and a screw 43. The solenoid 41 is connected to one end of the link member 44 by means of a rod 46. Calked at the other end of the link member 44 is a pin 47 which is to press the lever 19 at its end 19a. Also the lever 19 is pressed by an elastic member 48 secured to the frame piece 2 with a screw 49. Hence, the thread cutter blade 34 is energized upward in FIG. 1 and counterclockwise in FIG. 2.

The hole 11a of the shaft 11 is inserted with a spring 51 which abuts at one end on a screw 50 fixed in the frame piece 2 and at the other end on the leg portion 27a of the hinge screw 27. And the thread holder member 35 is energized by the spring 51 upward in FIG. 1 and counterclockwise in FIG. 2, as is the thread cutter blade described above.

An elastic member 53 attached to the frame piece 2 by a screw 52 is in engagement with an extension 15a of the slider 15 as illustrated in FIG. 4, thereby preventing the movement, leftward in FIG. 4, of the slider 15 due to the force of the spring 51. An L-shaped member 54 secured to the lever 19 by the screw 18 is designed to abut on the head ofthe hinge screw 27 fixed to the slider 15 while the lever 19 is working due to the force of the elastic member 48, so that said elastic member 53 is disengaged from the extension 15a of the slider 15.

- In the drawings, 55 designates a throat plate, N the upper thread leading to the needle (not shown) of the sewing machine, and B the under thread leading to the shuttle bobbin (not shown) of the shuttle race means 38.

The operations and functions of the embodiment of the invention illustrated in the attached drawings are described hereinbelow.

The standby condition of the thread cutting mechanism is illustrated in FIG. 6, with the thread cutter blade 34 and thread holder member 35 at their left ward positions due to the force of the elastic members 48 and 51. At the moment when the upper thread N encircles the shuttle race means 38 and is about to be pulled upward, as illustrated schematically in FIG. 6, the thread cutting mechanism sets in motion. At that moment, an electric current is flowed to the solenoid 41 attached to the lower surface of the table 40. Then, despite the force of the elastic member 48, the magnetic force of the solenoid 41 is conveyed via the rod 46, link member 44, lever 19 and link member 17 to the slider 14, which then sets the rotary member 20 revolving around the oscillating shaft 28. At the same time, the thread cutter blade 34 starts moving in the direction opposite to that of the rotation of the shuttle race means 38. And the slider 15, pushed by the slider 14, starts moving the thread holder member 35 in the direction opposite to that of the rotation of the shuttle race means 38 in spite of the spring 51, like the thread cutter blade 34.

As illustrated in FIG. 7 and 8, the protrusion 34a of the thread cutter blade and the protrusion 3411 (indicated in FIG. 10) of the thread holder member 35 thus moving in coordination, go through a loop of the upper thread N, thereby catching the needle-side part of the upper thread N at their indentations 34b and 35b. On the other hand, the other part of the loop of the upper thread N is caught at a recess 350 of the thread holder member 35 along with the under thread B. Succeedingly, the thread cutter blade 34 and the thread holder member 35 thus catching hold of the upper thread N and under thread B, further move on and stop at their positions illustrated in FIG. 9. The upper thread N, pulled upward by means ofa thread takeup lever (not shown), is tensed as it encircles the protrusion 35a as seen in FIG. 10, while the under thread B is tensed by the recess 35c of the thread holder member 35. And thus are both the upper thread N and the under thread B made ready to be cut.

The above condition marks an end of the first half of one complete thread-cutting cycle. At this moment, the extension 15a of the slider 15 is in engagement with the elastic member 53 as illustrated in FIG. 4, so that the slider 15 is prevented from returning to its initial position, as it is then not to be disengaged from the elastic member 53 only by the force of the spring 51 when the flow of the current to the solenoid 41 is stopped.

At the instant when the sewing machine is stopped with its needle bar (not shown) at its top dead center position, the flow of the current to the solenoid 41 is intercepted so that the thread cutter blade starts moving in the same direction as that of the rotation of the shuttle race means 38 due to the return force of the elastic member 48. The thread holder 35, on the other hand, is kept stopped with the upper thread N and under thread B at its recess 35c, since the slider 15 is locked by the elastic member 53 as mentioned above. Being tensed in this state, both the upper thread N and the under thread B are cut easily, leaving only minimum lengths at the end of the seam, but a cutting edge 34c of the thread cutter blade 34 which crosses the threads at an accelerated speed due to the force of the elastic member 48 (refer to FIGS. 11 and 12).

After thus cutting the threads, the thread cutter blade moves on toward its initial position. En route, the thread cutter blade causes the L-shaped member 54, attached to the lever 19, to strike against the head of the hinge screw 27 guiding the slider 15, as will be seen from FIG. 5 showing their relative locations. Due to the impact of this collision, the extension 15a of the slider 15 is disengaged from the elastic member 53, with a result that the slider 15 and therefore the thread holder member 35 start returning to their initial positions in succession to the thread cutter blade 34 due to the return force of the spring 51.

The complete thread-cutting cycle comes to an end as both the thread cutter blade 34 and the thread holder member 35 regain their initial standby positions illustrated in'FIG. 6. The upper thread N is then pulley up high enough to be kept securely inserted in the needle hole, and the under thread B has its desired length fed out of the thread holder member 35, for the ready start of the succeeding sewing work.

Although a specific embodiment of the invention has been shown and described in the foregoing, it will be obvious that the invention itself is not limited thereby but includes a latitude of modification, substitution and change coming within the spirit and scope of the invention herein.

What is claimed is:

1. In a sewing machine having a reciprocating needle and rotary shuttle race means, a thread cutter comprising in combination: a thread cutter blade for simultaneously cutting an upper and an under thread of the sewing machine, said thread cutter blade being capable of reciprocating above said shuttle race means concentrically with an oscillating shaft thereof; a thread holder member disposed in vertical relationship with said thread cutter blade so as to be capable of moving in coordination therewith; a pair of rotary members mounted at the end of a bush pivotally supporting said oscillating shaft and respectively attached with said thread cutter blade and said thread holder member; a pair of shaft-mounted sliders for moving said rotary members and therefore said thread cutter blade and said thread holder member attached thereto; means for actuating said sliders which then start moving said thread cutter blade and said thread holder member in the direction opposite to that of the rotation of said shuttle race means to the other extremity while getting hold of said upper thread and said under thread en route; a first elastic member attached to a frame piece for preventing said thread holder member for returning to its initial position by locking one of said sliders related therewith; a second elastic member similarly attached to said frame piece for returning said thread cutter blade to its initial position, said thread cutter blade on its way back cutting said upper thread and said under thread held together by said thread holder member; and means for unlocking said first elastic member from said one of the sliders thereby to permit said thread holder member to return to its initial position by means of a third elastic member.

2. A thread cutter as claimed in claim 1, wherein said thread cutter blade has an inwardly plane-angled cutting edge, and said thread holder member is recessed at one side, with such a relationship therebetween that said plane-angled cutting edge and said recessed side face each other when said thread cutter blade and said thread holder member are in superposition,

threads held together at said recess of the thread holder member.

3. A thread cutter as claimed in claim 2, wherein said thread cutter blade is approximately L-shaped at its leading part including said inwardly plane-angled cutting edge, and said thread holder member is formed with a protrusion shaped in part by said recess, the outward, angled protrusion of said L- shaped thread cutter blade and said protrusion of said thread holder member running together into the loop of the upper thread to get hold of it.

4. A thread cutter as claimed in claim 3, wherein said thread cutter blade and said thread holder member have both an indentation at their corresponding side, said indentations holding the needle side part of the loop of the upper thread.

5. A thread cutter as claimed in claim 1, wherein the shaft on which said sliders are mounted has a hole running lengthwise therethrough, said hole containing said third elastic member, and a longitudinal cutout slot for guiding said sliders and permitting the transmission of the force of said third elastic member to one of said sliders and thence to said thread holder member via one of said rotary members.

6. A thread cutter as claimed in claim 1, wherein said first elastic member is unlocked from said slider by means of an L- shaped member secured to a lever coupled rotatably with one end of a link member the other end of which is coupled rotatably with said slider related to said thread cutter blade, said lever being energized by said second elastic member during the return travel of said thread cutter blade so that said L- shaped member strikes against the head of a screw attached to said slider thereby to unlock the same from said first elastic member.

7. A thread cutter as claimed in claim 1, wherein said sliders are actuated by means of a solenoid. 

1. In a sewing machine having a reciprocating needle and rotary shuttle race means, a thread cutter comprising in combination: a thread cutter blade for simultaneously cutting an upper and an under thread of the sewing machine, said thread cutter blade being capable of reciprocating above said shuttle race means concentrically with an oscillating shaft thereof; a thread holder member disposed in vertical relationship with said thread cutter blade so as to be capable of moving in coordination therewith; a pair of rotary members mounted at the end of a bush pivotally supporting said oscillating shaft and respectively attached with said thread cutter blade and said thread holder member; a pair of shaft-mounted sliders for moving said rotary members and therefore said thread cutter blade and said thread holder member attached thereto; means for actuating said sliders which then start moving said thread cutter blade and said thread holder member in the direction opposite to that of the rotation of said shuttle race means to the other extremity while getting hold of said upper thread and said under thread en route; a first elastic member attached to a frame piece for preventing said thread holder member for returning to its initial position by locking one of said sliders related therewith; a second elastic member similarly attached to said frame piece for returning said thread cutter blade to its initial position, said thread cutter blade on its way back cutting said upper thread and said under thread held together by said thread holder member; and means for unlocking said first elastic member from said one of the sliders thereby to permit said thread holder member to return to its initial position by means of a third elastic member.
 2. A thread cutter as claimed in claim 1, wherein said thread cutter blade has an inwardly plane-angled cutting edge, and said thread holder member is recessed at one side, with such a relationship therebetween that said plane-angled cutting edge and said recessed side face each other when said thread cutter blade and said thread holder member are in superposition, said plane-angled cutting edge cutting the upper and under threads held together at said recess of the thread holder member.
 3. A thread cutter as claimed in claim 2, wherein said thread cutter blade is approximately L-shaped at its leading part including said inwardly plane-angled cutting edge, and said thread holder member is formed with a protrusion shaped in part by said recess, the outward, angled protrusion of said L-shaped thread cutter blade and said protrusion of said thread holder member running together into the loop of the upper thread to get hold of it.
 4. A thread cutter as claimed in claim 3, wherein said thread cutter blade and said thread holder member have both an indentation at their corresponding side, said indentations holding the needle side part of the loop of the upper thread.
 5. A thread cutter as claimed in claim 1, wherein the shaft on which said sliders are mounted has a hole running lengthwise therethrough, said hole containing said third elastic member, and a longitudinal cutout slot for guiding said sliders and permitting the transmission of the force of said third elastic member to one of said sliders and thence to said thread holder member via one of said rotary members.
 6. A thread cutter as claimed in claim 1, wherein said first elastic member is unlocked from said slider by means of an L-shaped member secured to a lever coupled rotatably with one end of a link member the other end of which is coupled rotatably with said slider related to said thread cutter blade, said lever being energized by said second elastic member during the return travel of said thread cutter blade so that said L-shaped member strikes against the head of a scrEw attached to said slider thereby to unlock the same from said first elastic member.
 7. A thread cutter as claimed in claim 1, wherein said sliders are actuated by means of a solenoid. 